Enhanced enums

enums.cpp

#define COUNT_(                                          \
  X64, X63, X62, X61, X60, X59, X58, X57, X56, X55, X54, \
  X53, X52, X51, X50, X49, X48, X47, X46, X45, X44, X43, \
  X42, X41, X40, X39, X38, X37, X36, X35, X34, X33, X32, \
  X31, X30, X29, X28, X27, X26, X25, X24, X23, X22, X21, \
  X20, X19, X18, X17, X16, X15, X14, X13, X12, X11, X10, \
  X9,   X8,  X7,  X6,  X5,  X4,  X3,  X2,  X1,   N,  ... \
) N
#define COUNT(...) COUNT_( __VA_ARGS__,       \
  64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, \
  53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, \
  42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, \
  31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, \
  20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, \
   9,  8,  7,  6,  5,  4,  3,  2,  1          \
)

#define STRINGIFY(X) #X
#define STRINGARG(X) #X,
#define EXPAND(X) X

#define HEAD(X, ...) (X)
#define TAIL(X, ...) (__VA_ARGS__)

#define FOREACH(MACRO, LIST) FOREACH_(COUNT LIST, MACRO, LIST)
#define FOREACH_(N, M, LIST) FOREACH__(N, M, LIST)
#define FOREACH__(N, M, LIST) FOREACH_##N(M, LIST)
#define FOREACH_1(M, LIST) M LIST
#define FOREACH_2(M, LIST)  EXPAND(M HEAD LIST) FOREACH_1(M, TAIL LIST)
#define FOREACH_3(M, LIST)  EXPAND(M HEAD LIST) FOREACH_2(M, TAIL LIST)
#define FOREACH_4(M, LIST)  EXPAND(M HEAD LIST) FOREACH_3(M, TAIL LIST)
#define FOREACH_5(M, LIST)  EXPAND(M HEAD LIST) FOREACH_4(M, TAIL LIST)
#define FOREACH_6(M, LIST)  EXPAND(M HEAD LIST) FOREACH_5(M, TAIL LIST)
#define FOREACH_7(M, LIST)  EXPAND(M HEAD LIST) FOREACH_6(M, TAIL LIST)
#define FOREACH_8(M, LIST)  EXPAND(M HEAD LIST) FOREACH_7(M, TAIL LIST)
#define FOREACH_9(M, LIST)  EXPAND(M HEAD LIST) FOREACH_8(M, TAIL LIST)
#define FOREACH_10(M, LIST) EXPAND(M HEAD LIST) FOREACH_9(M, TAIL LIST)
#define FOREACH_11(M, LIST) EXPAND(M HEAD LIST) FOREACH_10(M, TAIL LIST)
#define FOREACH_12(M, LIST) EXPAND(M HEAD LIST) FOREACH_11(M, TAIL LIST)
#define FOREACH_13(M, LIST) EXPAND(M HEAD LIST) FOREACH_12(M, TAIL LIST)
#define FOREACH_14(M, LIST) EXPAND(M HEAD LIST) FOREACH_13(M, TAIL LIST)
#define FOREACH_15(M, LIST) EXPAND(M HEAD LIST) FOREACH_14(M, TAIL LIST)
#define FOREACH_16(M, LIST) EXPAND(M HEAD LIST) FOREACH_15(M, TAIL LIST)
#define FOREACH_17(M, LIST) EXPAND(M HEAD LIST) FOREACH_16(M, TAIL LIST)
#define FOREACH_18(M, LIST) EXPAND(M HEAD LIST) FOREACH_17(M, TAIL LIST)
#define FOREACH_19(M, LIST) EXPAND(M HEAD LIST) FOREACH_18(M, TAIL LIST)
#define FOREACH_20(M, LIST) EXPAND(M HEAD LIST) FOREACH_19(M, TAIL LIST)
#define FOREACH_21(M, LIST) EXPAND(M HEAD LIST) FOREACH_20(M, TAIL LIST)
#define FOREACH_22(M, LIST) EXPAND(M HEAD LIST) FOREACH_21(M, TAIL LIST)
#define FOREACH_23(M, LIST) EXPAND(M HEAD LIST) FOREACH_22(M, TAIL LIST)
#define FOREACH_24(M, LIST) EXPAND(M HEAD LIST) FOREACH_23(M, TAIL LIST)
#define FOREACH_25(M, LIST) EXPAND(M HEAD LIST) FOREACH_24(M, TAIL LIST)
#define FOREACH_26(M, LIST) EXPAND(M HEAD LIST) FOREACH_25(M, TAIL LIST)
#define FOREACH_27(M, LIST) EXPAND(M HEAD LIST) FOREACH_26(M, TAIL LIST)
#define FOREACH_28(M, LIST) EXPAND(M HEAD LIST) FOREACH_27(M, TAIL LIST)
#define FOREACH_29(M, LIST) EXPAND(M HEAD LIST) FOREACH_28(M, TAIL LIST)
#define FOREACH_30(M, LIST) EXPAND(M HEAD LIST) FOREACH_29(M, TAIL LIST)
#define FOREACH_31(M, LIST) EXPAND(M HEAD LIST) FOREACH_30(M, TAIL LIST)
#define FOREACH_32(M, LIST) EXPAND(M HEAD LIST) FOREACH_31(M, TAIL LIST)
#define FOREACH_33(M, LIST) EXPAND(M HEAD LIST) FOREACH_32(M, TAIL LIST)
#define FOREACH_34(M, LIST) EXPAND(M HEAD LIST) FOREACH_33(M, TAIL LIST)
#define FOREACH_35(M, LIST) EXPAND(M HEAD LIST) FOREACH_34(M, TAIL LIST)
#define FOREACH_36(M, LIST) EXPAND(M HEAD LIST) FOREACH_35(M, TAIL LIST)
#define FOREACH_37(M, LIST) EXPAND(M HEAD LIST) FOREACH_36(M, TAIL LIST)
#define FOREACH_38(M, LIST) EXPAND(M HEAD LIST) FOREACH_37(M, TAIL LIST)
#define FOREACH_39(M, LIST) EXPAND(M HEAD LIST) FOREACH_38(M, TAIL LIST)
#define FOREACH_40(M, LIST) EXPAND(M HEAD LIST) FOREACH_39(M, TAIL LIST)
#define FOREACH_41(M, LIST) EXPAND(M HEAD LIST) FOREACH_40(M, TAIL LIST)
#define FOREACH_42(M, LIST) EXPAND(M HEAD LIST) FOREACH_41(M, TAIL LIST)
#define FOREACH_43(M, LIST) EXPAND(M HEAD LIST) FOREACH_42(M, TAIL LIST)
#define FOREACH_44(M, LIST) EXPAND(M HEAD LIST) FOREACH_43(M, TAIL LIST)
#define FOREACH_45(M, LIST) EXPAND(M HEAD LIST) FOREACH_44(M, TAIL LIST)
#define FOREACH_46(M, LIST) EXPAND(M HEAD LIST) FOREACH_45(M, TAIL LIST)
#define FOREACH_47(M, LIST) EXPAND(M HEAD LIST) FOREACH_46(M, TAIL LIST)
#define FOREACH_48(M, LIST) EXPAND(M HEAD LIST) FOREACH_47(M, TAIL LIST)
#define FOREACH_49(M, LIST) EXPAND(M HEAD LIST) FOREACH_48(M, TAIL LIST)
#define FOREACH_50(M, LIST) EXPAND(M HEAD LIST) FOREACH_49(M, TAIL LIST)
#define FOREACH_51(M, LIST) EXPAND(M HEAD LIST) FOREACH_50(M, TAIL LIST)
#define FOREACH_52(M, LIST) EXPAND(M HEAD LIST) FOREACH_51(M, TAIL LIST)
#define FOREACH_53(M, LIST) EXPAND(M HEAD LIST) FOREACH_52(M, TAIL LIST)
#define FOREACH_54(M, LIST) EXPAND(M HEAD LIST) FOREACH_53(M, TAIL LIST)
#define FOREACH_55(M, LIST) EXPAND(M HEAD LIST) FOREACH_54(M, TAIL LIST)
#define FOREACH_56(M, LIST) EXPAND(M HEAD LIST) FOREACH_55(M, TAIL LIST)
#define FOREACH_57(M, LIST) EXPAND(M HEAD LIST) FOREACH_56(M, TAIL LIST)
#define FOREACH_58(M, LIST) EXPAND(M HEAD LIST) FOREACH_57(M, TAIL LIST)
#define FOREACH_59(M, LIST) EXPAND(M HEAD LIST) FOREACH_58(M, TAIL LIST)
#define FOREACH_60(M, LIST) EXPAND(M HEAD LIST) FOREACH_59(M, TAIL LIST)
#define FOREACH_61(M, LIST) EXPAND(M HEAD LIST) FOREACH_60(M, TAIL LIST)
#define FOREACH_62(M, LIST) EXPAND(M HEAD LIST) FOREACH_61(M, TAIL LIST)
#define FOREACH_63(M, LIST) EXPAND(M HEAD LIST) FOREACH_62(M, TAIL LIST)
#define FOREACH_64(M, LIST) EXPAND(M HEAD LIST) FOREACH_63(M, TAIL LIST)


#include <ostream>
#include <iterator>
#include <utility>


template<typename T> class enum_iterator;

template<typename T>
static constexpr std::size_t enum_count = get_count(T{});

template<typename T>
static const enum_iterator<T> enum_iterate = enum_iterator<T>{};

template<typename T>
class enum_iterator {
    explicit enum_iterator(std::size_t i) noexcept : pos_{i} {}

    std::size_t pos_;

public:
    using iterator_category = std::input_iterator_tag;
    using value_type = T;
    using difference_type = void;
    using pointer = T*;
    using reference = T&;

    explicit enum_iterator(T const& t={}) noexcept
            : pos_{static_cast<std::size_t>(t)}
    {}

    value_type operator*() const noexcept { return static_cast<T>(pos_); }
    enum_iterator operator++() noexcept { return enum_iterator{++pos_}; }
    enum_iterator operator++(int) noexcept { return enum_iterator{pos_++}; }

    bool operator==(enum_iterator const& i) noexcept { return i.pos_ == pos_; }
    bool operator!=(enum_iterator const& i) noexcept { return i.pos_ != pos_; }

    static enum_iterator cbegin() noexcept { return enum_iterator{T{}}; }
    static enum_iterator begin() noexcept { return enum_iterator{T{}}; }
    static enum_iterator cend() noexcept { return enum_iterator{enum_count<T>}; }
    static enum_iterator end() noexcept { return enum_iterator{enum_count<T>}; }
};


#define ENUM(NAME, ...)                                      \
enum class NAME : std::size_t {                              \
    __VA_ARGS__                                              \
};                                                           \
static constexpr char const* NAME##_names_[] = {             \
    FOREACH(STRINGARG, (__VA_ARGS__))                        \
};                                                           \
inline constexpr std::size_t get_count(NAME) noexcept {      \
    return COUNT(__VA_ARGS__);                               \
}                                                            \
inline constexpr char const* to_string(NAME e) noexcept {    \
    return NAME##_names_[static_cast<std::size_t>(e)];       \
}                                                            \
inline std::ostream& operator<<(std::ostream& os, NAME e) {  \
    return os << NAME##_names_[static_cast<std::size_t>(e)]; \
}


/*
  Features:

  ENUM(numbers, one, two, three)      // create the enum
  enum_count<numbers>                 // get number of elements
  for (auto n : enum_count<numbers>)  // iterate over elements
  to_string(numbers::one)             // convert to c string
  std::cout << numbers::two           // print
*/

#include <iostream>

namespace test {
    ENUM(numbers, one, two, three)
}

int main() {
    for (auto n : enum_iterate<test::numbers>)
        std::cout << n << std::endl;
    return 0;
}